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In the context of climate change and the ongoing population growth, current agriculture inevitably faces many challenges. Long periods of drought are often followed by shorter periods of heavy precipitation and degraded soil is often unable to retain the rainfall water properly. Apart from common organic fertilizers, soil amendments are currently considered a promising solution that might improve soil quality. The most discussed one is biochar, a natural soil conditioner that might under certain conditions improve soil properties. This study is based on the experiment that was established in 2017 in order to determine the impact of biochar dosage and it's effect over time. Four parcels approximately 15×30 m were designed in Rapotín, Czech Republic. Each of them was treated with a specific dose of biochar (15, 30, 45, 60 t ha-1), and selected soil physical properties such as penetration resistance and reduced bulk density were then measured at the beginning of the cropping season 2019. In addition, vegetation properties were investigated with the use of handheld sensors repeatedly during the season on winter wheat. The dataset contained information about chlorophyll and nitrogen content as well as Normalized Difference Vegetation Index estimations. Acquired values were later compared with the results obtained from the fifth variant founded in 2014 with a 15 t ha-1 dose and from the control variant. Although the dosage levels applied were quite substantial, no significant difference was found when evaluating selected soil properties. Crop response gave similar results. Any of the examined characteristics differed among the 2017 variants and control. Nevertheless, when compared to the 2014 variant, clearly different results were detected. Thus, this study concluded that the effect of biochar dosage is might not be as significant factor, however, the time effect likely is. Therefore, the study has to continue and soil/crop properties will be observed in the upcoming season as well. [ABSTRACT FROM AUTHOR]

Due to intensified agricultural mechanization, soils are exposed to increased levels of degradation. Soil compaction is the beginning of this degradation which further proceeds to decrease organic matter content of soils. Among the various methods applied to solve these problems, the addition of organic matter to the soil has an important place. Thus, agricultural land application of organic wastes, such as biochar and compost, could alter the soil properties to offset the degradation effects. The aim of this research was to determine the effect of compost and biochar application on the soil compaction and its quality score. Biochar and compost of the Elaeagnus tree pruning residues were applied in a field at a similar rate of 0%, 2%, and 4%. Results indicated that the soil penetration resistance (PR) statistically experienced a downward trend compared to the control when applied with compost and biochar. The application of 2–4% biochar and compost lowered soil PR by exactly 8.80%, 9.33%, 18.22%, and 28.89%, respectively, throughout the period of 7 months. Furthermore, the infusion of biochar and compost into the soil significantly increased the soil compaction quality score compared to the control, and the least value of PR was observed for the compost-treated soil at the application rate of 4%. Compost and biochar applications were effective to improve the physical quality of a sandy clay loam soil, making it more suitable for plant development. On the other hand, the effect of compost treatments was more impact than biochar treatments. [ABSTRACT FROM AUTHOR]

Biochar (BC) has been reported to improve a number of soil structural and hydraulic properties but detailed studies are scant on how BC affects crust formation, penetration resistance, water repellency and saturated hydraulic conductivity (K sat ). The objective of this study was to quantify the effect of maize cob BC of three different particle sizes on soil crusting (penetration resistance), water repellency, and K sat of loamy fine sand and sandy loam in Zambia. The BC particle sizes were <0.5 and 1–5 mm applied at 17.5 and 35 t ha −1 in the two soils and intermediate size of 0.5–1 mm applied at lower rates (17.5 and 28 t ha −1 in the loamy fine sand and 13.3 and 26.7 t ha −1 in the sandy loam). Water repellency included both water drop penetration time (WDPT) and minimum molarity of the ethanol droplet at which rapid infiltration into the soil occurs. The BC was produced by slow pyrolysis of corn cobs at a temperature of 350 °C. Biochar, added homogeneously to the upper 7 cm of the soil, reduced the penetration resistance of surface soil of sandy loam with both the crust intact (−2.1 ± 0.6 N cm −2 per percent BC added; p = 0.001 in March 2015 and slightly smaller in October 2014) and the crust removed (−2.9 ± 0.6 N cm −2 per percent BC added; p = 0.0001). This effect occurred irrespective of particle size of BC (p > 0.05). No effect of BC on penetration resistance was found in the loamy fine sand (p > 0.05). In dry sandy loam with moisture content <1% v/v, the proportion of wettable crusted surface was significantly smaller (25%) than in moist soil (98%) with moisture content of ∼ 10% v/v. Only fine BC of <0.5 mm increased WDPT of the crusted surface of sandy loam (p < 0.05), reducing the proportion of wettable surface from 98 to 80% in moist soil and from 25 to 18% in dry soil. Coarser BCs, instead, increased the proportion of wettable crusted surface from 25% to 45% and 90% for 3% 0.5–1 mm BC and 4% 1–5 mm BC addition, respectively, in dry soil. Biochar significantly reduced K sat (p < 0.05) in sandy loam below the crust by 0.17 ± 0.07 cm h −1 per percent BC added. However, no effect was found in loamy fine sand. Since BC amended sandy loam below the crust showed no water repellency, reduction in K sat cannot be explained by water-repellent nature of BC. Instead, this may be due to clogging of soil pores by BC or to collapse of soil structure near water saturation. [ABSTRACT FROM AUTHOR]

Biochar is proven to enhance soil fertility and increase crop productivity. Given that the influence of biochar on soil compaction remains unclear, selected physico-mechanical properties of soil amended with wood-derived biochar were assessed. For unamended silt loam, the bulk density, maximum bulk density, optimum moisture content, plastic limit, liquid limit, and plasticity index were 1.05 Mg m-3, 1.69 Mg m-3, 16.55, 17.1, 29.3, and 12.2%, respectively. The penetration resistance and shear strength of the unamended silt loam compacted in the standard compaction Proctor mold and at its optimum moisture content were 1800 kPa and 850 kPa, respectively. Results from amending the silt loam with 10% particle size ranges (0.5-212 µm) led to relative decreases of 18.1, 17.75, 66.66, and 97.4% in bulk density, maximum bulk density, penetration resistance, and shear strength, respectively; a 26.8% relative increase in optimum moisture content; along with absolute increases in plastic limit, liquid limit, and plasticity index of 5.3, 13.7, and 8.4%, respectively. While the biochar-amended silt loam soil was more susceptible to compaction, however, soil mechanical impedance enhanced. [ABSTRACT FROM AUTHOR]

• Biochar changes most soil compaction parameters but benefits may last <2 years. • Soil without biochar can be compacted at lower water content than soil with biochar. • At least 10 Mg biochar ha−1 may be needed to significantly reduce soil compaction. • Biochar can complement other organic amendments for reducing soil compaction. • Biochar can alleviate soil compaction but more long-term field data are needed. Biochar is considered to enhance numerous soil ecosystem services, but whether it alleviates soil compaction is not well known. This paper: 1) synthesizes the biochar impacts on soil compaction parameters including bulk density, penetration resistance, aggregate tensile strength, Proctor maximum bulk density (soil compactability), and the water content at which the Proctor maximum bulk density occurs (critical water content), 2) discusses potential factors affecting biochar performance, and 3) compares the impacts of biochar on soil compaction with those of other amendments. Literature indicates that biochar generally reduces bulk density, tensile strength, and Proctor maximum bulk density; and increases the critical water content but may or may not reduce penetration resistance. Biochar reduces bulk density from −1% to −20% (-8.8% average), tensile strength from −8 to −72% (-31% average), and Proctor maximum bulk density from −1 to −19% (-9.3% average), whereas it increases the critical water content from 1 to 64% (21% average). The increase in critical water content suggests soils with biochar can be trafficked at higher water content without causing compaction than soils without biochar. An increase in biochar application rate reduces soil compaction and explains 11% to 63% of the variability in compaction parameters, but biochar benefits can be short-lived (<2 yr). It appears that, in general, at least 10 Mg ha−1 of biochar are needed to significantly reduce compaction. Larger application rates (>20 Mg ha−1) can be needed for reducing penetration resistance and Proctor maximum bulk density than for other compaction parameters. Biochar has similar benefits to manure for reducing soil bulk density and can complement other organic amendments for reducing soil compaction. How biochar feedstock, pyrolysis temperature; and companion amendments; and soil texture influence biochar impacts on compaction is still unclear. Overall, biochar has the potential to alleviate soil compaction, but more long-term field data, particularly on penetration resistance, Proctor maximum bulk density, and critical water content for multiple biochar application rates, feedstocks, pyrolysis temperature; and amendments are needed to better elucidate biochar effects, biochar longevity, and optimum levels of biochar application. [ABSTRACT FROM AUTHOR]